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Viscosity of high-K basalt from the 5th April 2003 Stromboli paroxysmal explosion
Author(s)
Language
English
Obiettivo Specifico
2.3. TTC - Laboratori di chimica e fisica delle rocce
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/260 (2009)
Publisher
elsevier
Pages (printed)
278-285
Issued date
2009
Abstract
The 5th April 2003 paroxysmal event was the strongest explosion that has occurred at Stromboli in the last
50 years. This event lasted only few minutes and was characterised by two violent explosions, followed by gas
and pyroclast emission. In order to constrain models of the dynamics of the paroxystic event the viscosity of
anhydrous and hydrous Stromboli high potassium (HK)-basaltic melts have been measured. Viscosity has been
investigated in the low viscosity range with the falling sphere method at superliquidus temperatures (1423 to
1673 K) and 0.5 GPa and in the high viscosity range with micropenetration near the glass transition
temperature (723 to 1035 K) at atmospheric pressure. Falling sphere experiments were performed in a piston
cylinder apparatus with melts whose water content varies from nominally anhydrous (0.02 wt.% H2O) to
4.16 wt.% H2O. The combination of high- and low-viscosity data permits a general description of the viscosity as
a function of temperature and water contentusing a modified Tamman–Vogel–Fulcher equation. Using these
new viscosity data, an estimation of the flow regime and magma velocity is performed. Our data suggest that
the ascent of magma from the 7–8 km deep reservoir to a shallower reservoir located at about 3 km of depth,
may occur within minutes. Moreover, we infer a turbulent flow regime. Finally, our estimates of the ascent
velocity agree qualitatively with results from petrological studies (e.g. [Bertagnini, A., Métrich, N., Landi, P.,
Rosi, M., 2003. Stromboli volcano (Aeolian Archipelago, Italy): an openwindowon the deep-feeding system of a
steady state basaltic volcano. Journal of Geophysical Research 108, 2336–2350.]), which indicate a turbulent
flow regime and rapid ascent velocities such to inhibit volatile-loss-induced crystallization.We conclude that
hazard evaluation at Stromboli Island should incorporate the likelihood of very rapid ascent of less-evolved
melts from depth.
50 years. This event lasted only few minutes and was characterised by two violent explosions, followed by gas
and pyroclast emission. In order to constrain models of the dynamics of the paroxystic event the viscosity of
anhydrous and hydrous Stromboli high potassium (HK)-basaltic melts have been measured. Viscosity has been
investigated in the low viscosity range with the falling sphere method at superliquidus temperatures (1423 to
1673 K) and 0.5 GPa and in the high viscosity range with micropenetration near the glass transition
temperature (723 to 1035 K) at atmospheric pressure. Falling sphere experiments were performed in a piston
cylinder apparatus with melts whose water content varies from nominally anhydrous (0.02 wt.% H2O) to
4.16 wt.% H2O. The combination of high- and low-viscosity data permits a general description of the viscosity as
a function of temperature and water contentusing a modified Tamman–Vogel–Fulcher equation. Using these
new viscosity data, an estimation of the flow regime and magma velocity is performed. Our data suggest that
the ascent of magma from the 7–8 km deep reservoir to a shallower reservoir located at about 3 km of depth,
may occur within minutes. Moreover, we infer a turbulent flow regime. Finally, our estimates of the ascent
velocity agree qualitatively with results from petrological studies (e.g. [Bertagnini, A., Métrich, N., Landi, P.,
Rosi, M., 2003. Stromboli volcano (Aeolian Archipelago, Italy): an openwindowon the deep-feeding system of a
steady state basaltic volcano. Journal of Geophysical Research 108, 2336–2350.]), which indicate a turbulent
flow regime and rapid ascent velocities such to inhibit volatile-loss-induced crystallization.We conclude that
hazard evaluation at Stromboli Island should incorporate the likelihood of very rapid ascent of less-evolved
melts from depth.
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